Application of precipitates of methylene-ureas and products obtained

ABSTRACT

A method of manufacture from a pre-determined material, especially of a synthetic or fibrous type, of a material, in particular a paper for reproduction, which combines superior qualities of whiteness, opacity, thermal stability, insolubility and lightness, said method consisting of loading said material, throughout its mass or superficially, by means of a filler product having a base of a methylene-ureas precipitate with a low degree of polymerization, obtained by the reaction of urea on formaldehyde in an acid medium.

Minted States Patent 11 1 1111 3,869,311 Jacquelin et a1. Mar. 4, 1975 [5 APPLICATION OF PRECIPITATES 0F 2,652,374 9/1953 Thompson 117/155 x METHYLENE UREAS AND PRODUCTS 2,851,424 9/1958 Switzer et a1, l17/33.5 X OBTAINED 2,956,898 10/1960 Fleck 1l7/33.5 3,018,287 1/1962 Fleck 117/33.5 X [75] Inventors: Guy Jacquelin; Solange Sangenis, 3,181,950 5/1965 Koerber et a1 117/33.5 X

both of Grenoble, France [73] Assignee: Centre Technique de lllndustrie des Primary Examiner-Michael R. Lusignan Papiers Cartons et celluloses, l ere, Attorney, Agent, or Firm-Charles E. Baxley, Esq. France [22] F1led: May 28, 1970 [57] ABSTRACT 21 A 1. N 41,374 1 pp 0 A method of manufacture from a pre-determmed material, especially of a synthetic or fibrous type, of a 1 g" Appllcatlon y Data material, in particular a paper for reproduction, which June 3, 1969 France 69.18236 Combines superior qualities of whiteness, opacity, thermal stability, insolubility and lightness, said [52] US. Cl. 117/155 L, 117/33.5 T, 117/154 method consisting ofloading said material, throughout [51] Int. Cl D21h 1/28 its mass or superficially, by means of a filler product [58] Field of Search 117/154, 155 L, 33.5 T having a base of a methylene-ureas precipitate with a low degree of polymerization, obtained by the reac- [56] References Cited tion of urea on formaldehyde in an acid medium. UNITED STATES PATENTS 3 Cl 4 D F 2399489 4/1946 aims, rawmg lgures Landes 117/155 X APPLICATION OF PRECIPITATES OF METHYLENE-UREAS AND PRODUCTS OBTAINED The present invention relates to a method of preparation, from a pre-determined material, in particular synthetic or fibrous, of a substance which combines high qualities of whiteness, opacity in the visible spectrum, transparency to ultra-violet rays, stability to light and heat, insolubility and lightness. This method is more particularly intended to be applied to the manufacture of special papers: paper for reproduction, printing, absorbent papers.

The invention also relates to a material, in particular a paper, obtained by the above-mentioned method.

The condensation products of urea and formaldehyde have formed the subject of numerous studies, and theindustrial products manufactured from these reactants are also numerous: according to the relative proportions of urea and formol, and the conditions of reaction, there are obtained resins for moulding, adhesives, adjuvants for textiles, paper-making, etc. However, for these manufactures, the reactants are utilized in a slightly acid medium. In fact, in a highly-acid medium there are formed white precipitates of methylene-ureas having a low degree of polymerization, known as Goldschmidt" products which are undesirable for these manufactures.

The Applicants having brought into evidence these special characteristics of whiteness, opacity in the visible spectrum, transparency to ultra-violet rays, stability to light and to heat, insolubility and lightness which are possessed by these precipitates have discovered a new application of these latter. They have developed a method of manufacture from a pre-determined material, especially synthetic or fibrous, of a substance which combines the superior qualities mentioned above.

The method according to the invention consists of charging the said material, throughout its mass or superficially, with a filler product having a base of a precipitate of methylene-ureas having a low degree of polymerization, obtained by the reaction of urea on formaldehyde in an acid medium.

This filler product permits the above-mentioned characteristics to be given to the base material and produces a substance having advantageous qualities for various branches of the technical art, especially the branch of synthetic materials or paper-making products. The filler product with a base of precipitate of methylene-ureas is particularly suitable to this latter case, due to its opacity to visible light and its transparency to ultra-violet rays. In fact, certain special papers for reproduction necessitate good opacity to visible light, combined with maximum transparency to ultraviolet rays. In addition, its physical characteristics per mit a matt appearance to be obtained in the paper, this appearance being desirable for certain printing papers.

In the application to paper-making products of the method of manufacture according to the invention, the filler product is preferably applied in the form of a su-' perficial coating on a paper support and is composed of an aqueous suspension ofa precipitate of methyleneureas and the binders and adjuvants usually employed in coating compositions: dispersing agent, casein, latex of the styrene butadiene type or the like. The material obtained is a printing paper which has especially qualities of opacity, whiteness and matt surface which are improved for a reduced weight as compared with standard papers, and in particular papers coated with compositions having a kaolin base.

A comparison of the same paper support coated on the one hand with the composition according to the invention and on the other hand with a conventional composition with a base of kaolin makes it possible to bring into evidence, for an equal weight of coating per unit surface, a substantial increase in whiteness in the case of the formol-urea precipitate. The opacities are very close in the two cases, but the effect of calendering the paper is, from the point of view of optical characteristics, unfavourable to the composition with a base of kaolin, whereas it does not modify the optical characteristics of the coating with a base of formol-urea precipitates.

In addition, for equal proportions by weight of binder, the resistance to tearing of the coatings with a base of formol-urea precipitate is higher or equal to that of the coatings with a base of kaolin; for an equal volumetric concentration of pigment, this strength is greater in the case of coatings with a base of formolurea precipitate.

By way of example, there is given below the composition ofa surface coating which may, amongst others, be applied on a paper AFNOR IV: parts of formolurea precipitate, 15 parts of casein, 10 parts of styrenebutadiene latex and 0.6 parts of dispersant in suspension in 293 parts of water.

The content of dry material in a composition of this kind is approximately equal to 30% and its Brookfield viscosity (axis No. l, 100 rpm.) is 80 centipoises.

There are given below two methods of manufacture with a good yield, ofa formol-urea precipitate. The first method consists in carrying out the following operations in order to obtain 355.3 grams of precipitate:

Add 228 cu.cm. of water and 1055 grams of a 20% urea solution (dry weight of urea 316.5 grams) to 496.7 grams of a formaldehyde solution, having 30.2% by weight of HCHO (weight of pure HCHO 150 grams) and the pH value of which has been adjusted to 6.2 by the addition of a decinormal base, especially of soda. In these conditions, the pH value of the mixture is 8.8, the temperature is 204C. and the formaldehyde/urea ratio is 0.47 by weight and 0.95 in mols;

Leave the mixed product to react at ambient temperature for min. with moderate stirring; the pH value then becomes 8.0 and the temperature rises to 23.6C.;

Add 2 litres of water and 750 cu.cm. of normal acid, especially hydrochloric acid; this dilution and acidification cause an increase in temperature which reaches a maximum of 313C. at the end of about 12 minutes;

Allow the products to react, with moderate stirring. for 60 minutes; during the course of this reaction, the pH value is approximately equal to 1;

Filter and wash the precipitate obtained until it is neutral, and then dry it, especially in a ventilated stove at l00l05C., until the weight is constant.

Under these conditions there are obtained 355.3 grams of precipitate which represent 76.2% of the total initial weight of urea and formaldehyde.

The other method of manufacture, with an almost identical yield, consists in carrying out the following operations in order to obtain 237 grams of precipitate:

Add 80 cu.cm. of water, 200 grams of dry urea and 1.5 grams of a dispersing agent to 353.4 grams of a formaldehyde solution having 28.3% by weight of HCHO (weight of pure formaldehyde 100 grams) and in which the pH value has been adjusted to 6.3 by the addition of a decinormal base, especially of soda. Under these conditions, the formaldehyde/urea ratio is 0.5 by weight and 1.0 in mols;

Stir the reaction medium for minutes; the solution of the urea is accompanied by a fall in temperature to about 6C.;

Add 27.4 cu.cm. of a twice normal acid solution, es-

pecially of hydrochloric acid, and stir the mixture violently. A white precipitate is formed a few minutes after acidification; the reaction is exothermic and the temperature reaches 73C. at the end of about 9 minutes;

After this time (9 minutes) cool the mixture obtained by pouring it into a large volume of cold water;

Filter, wash and dry the precipitate in the same way as for the method already described.

There are thus obtained 237 grams of precipitate, which corresponds to 79% of the initial weight of urea and formaldehyde.

It will of course be understood that the various values given for these methods of manufacture can be subject two modifications: in particular, the granular size of the product obtained can be regulated by acting on the concentrations, the temperature and the stirring of the medium at the moment of acidification.

The precipitate of methylene-ureas obtained especially by these methods of preparation, appear in the form of small spheres exhibiting the optical phenomenon of the Maltese cross, similar to that which is observed on grains of native starch, with a stratified structure. The physical characteristics of this precipitate are as follows:

Melting point comprised between 235 and 250C.;

Volume-mass comprised between 1.00 and 1.70

grams per cu.cm.;

pH value of the isoelectric point comprised between 4 and 7;

Proportion of nitrogen (Kjeldahl) comprised between 30 and 38%.

The index of refraction of this precipitate is comprised between 1.4 and 1.6; the following Table gives the factor of diffuse reflection for two precipitates, one corresponding to a molar ratio of formaldehyde/urea of 0.95, the other to a ratio of 1.9. The measurements were made by means of an Elrepho photometer calibrated with respect to MgO by taking 100% as the reflection factor for MgO.

Furthermore, the whiteness index measured under the same conditions with a filter R 457 is equal to 98.2 for the first precipitate and 96.4 for the second.

It should be observed that these precipitates of methylene-ureas may also be obtained by more direct syntheses involving for example the use of a direct reaction of carbon monoxide on ammonia at high pressure in the presence of a catalyst.

The invention also relates to a paper, particularly intended for printing and manufactured by the method described above; according to the invention, this paper is charged with a superficial coating layer with a base of a methylene-ureas precipitate.

By way of illustration, there is given below the composition ofa coating paste together with the properties of the coated paper obtained.

The support paper for the coating may be for example an AFNOR IV paper and the composition by weight of the surface coating is as follows:

parts of formol-urea precipitate;

15 parts of casein;

10 parts of styrene-butadiene latex;

0.6 part of a dispersing agent;

293 parts of water.

Reference will now be made to the accompanying drawings in order to appreciate the properties of the coated paper obtained. In these drawings, FIG. 1 represents:

A curve A giving the whiteness of the abovementioned paper, not calendered, as a function of the dry weight of deposited coating (in g/sq.m.);

A curve A, giving the whiteness of the above paper,

calendered, as a function of the dry weight of coating deposited (in g/sq.m.);

A curve B giving by way of comparison the whiteness of a non-calendered paper obtained by coating, on an identical paper support, with a standard composition with a base of kaolin having an equal proportion of binder by weight;

A curve B giving the whiteness of this latter paper after calendering.

The calendering operations were carried out by three passes through the Ramisch calender (two tonnes).

By comparison of these curves, it is noted that the calendering has a very slight influence on the papers according to the invention, since the curves A and A are practically coincident. There is also observed a substantial gain in whiteness, for equal weights of coating, in the case of the use of the formol-urea precipitate as a coating.

FIG. 2 shows curves C, C D and D, giving the opacity on a white ground of the four cases of papers referred to above, as a function of the dry weight of coating deposited (in g/sq.m.).

From these curves it can be seen that the opacities are very close for non-calendered papers coated with formolurea precipitate or with kaolin. However, the effect of the calendering is slightly unfavourable to the composition with a kaolin base, whereas it practically does not modify the optical characteristics of the paper with a base of the formol-urea precipitate.

In addition, the papers coated by a filler product with a base of formol-urea precipitate have a high microporosity, but also a macro-porosity which may be high.

Furthermore, the transparency to ultra-violet rays of this filler material makes it possible to obtain a high efficiency with optical blueing agents. Thus, the coating composition maycomprise up to 1.5% of these agents by weight of the filler introduced.

According to a preferred method of addition of the blueing agent, the latter is fixed on the methylene-ureas at the time of manufacture of this latter.

FIG. 3 represents:

A curve E giving, as a function of the maximum wave-length, the diffused reflection factor of a paper coated with 13.5 of a coating with a base of formo1-urea precipitate, without optical blueing agent;

A curve E,, giving, as a function of the maximum wave-length, the diffuse reflection factor of a paper coated with the same weight of a coating with a base of formol-urea precipitate containing 0.87% of optical blueing agent with respect to the dry extract of the coating bath;

By way of comparison, curves F and F similar to the curves E and E, for a paper with a coating ofa kaolin base;

These measurements were carried out with Xenon lighting.

By means of these curves, it can be seen that for an equal weight of coating deposited, the optical blueing agent is more effective when the filler has a base of formolurea precipitate.

This conclusion is confirmed by FIG. 4, which represents:

A curve G14 giving, as a function of the proportion of optical blueing agent with respect to the dry mate rials of the coating baths, the diffuse reflection factor of a paper coated with 14 g/sq.m. of a coating with a base of formol-urea precipitate;

A similar curve G for a paper coated with 22 g/sq.m. of the same coating;

By way of comparison, curves H and H similar to the curves (3,, and G but for a coating with a base of kaolin.

. These measurements were carried out with Xenon lighting in the presence of a filter R 457.

The optical blueing agent is more effective in the case ofa coating with a base of formol-urea precipitate, the difference being greater as the thickness of the coating is increased.

To the characteristics enumerated are added other properties ofpapers with coatings having a base of formolurea precipitate, such as for example their fireproofing, anti-parasitic and anti-cryptogamic properties.

In addition, it will be noted that the formolurea precipitates are relatively economical materials. This ad vantage is accentuated, by reason of their low density in comparison with mineral fillers which are two or three times more dense; for equal weights, the effective surface coated by coatings with a base of formol-urea precipitate is greater. This factor is particularly advantageous for papers intended for printing, for which increased lightness is desired for a given opacity.

It will of course be understood that the present invention is not limited to the terms of the foregoing description, but will comprise on the contrary all the alternative forms and improvements within the scope of those skilled in the art. In particular, there may be applied in identically the same way, similar precipitates obtained from neighbouring chemical constituents, in particular derivatives of urea such as thiourea, biuret dicyanodiamide, guanidine, phenyl-urea, etc. These products may be employed instead of the urea or in a mixture with this substance.

Similarly, another aldehyde may be partly substituted for the formaldehyde.

What we claim is:

1. A paper to which has been applied a filler product having as a base an insoluble and pulverulent methylene urea precipitate having a low degree of polymerization, the methylene urea precipitate having the following properties:

index of refraction between about 1.4 to 1.6,

diffuse reflection factor higher than for an illumination of maximum wavelength between about 0.42 to 0.68 microns,

melting point between about 230 to 250C,

volume-mass between about 1.00 to 1.70 g/cu.cm.,'

pH value of the isoelectric point between about 4 to 7, and

a percent of nitrogen between about 30 and 38%.

2. A paper according to claim I wherein the filler product consists in parts by weight of parts methylene-urea precipitate,

15 parts casein,

10 parts styrene-butadiene latex,

0.6 part dispersing agent, and

293 parts water.

3. A paper according to claim 1 wherein the filler product is coated on the paper. 

1. A PAPER TO WHICH HAS BEEN APPLIED A FILLER PRODUCT HAVING AS A BASE AN INSOLUBLE AND PULVERULENT METHYLENE UREA PRECIPITATE HAVING A LOW DEGREE OF POLYMERIZATION, THE METHYLENE UREA PRECIPITATE HAVING THE FOLLOWING PROPERTIES: INDEX OF REFRACTION BETWEEN ABOUT 1.4 TO 1.6, DIFFUSE REFLECTION FACTOR HIGHER THAN 95% FOR AN ILLUMINATION OF MAXIMUM WAVELENGTH BETWEEN ABOUT 0.45 TO 0.68 MICRONS, MELTING POINT BETWEEN ABOUT 230* TO 250*C., VOLUME-MASS BETWEEN ABOUT 1.00 TO 1.70 G/CU.CM., PH VALUE OF THE ISOELECTRIC POINT BETWEEN ABOUT 4 TO 7, AND A PERCENT OF NITROGEN BETWEEN ABOUT 30 AND 38%.
 2. A paper according to claim 1 wherein the filler product consists in parts by weight of 100 parts methylene-urea precipitate, 15 parts casein, 10 parts styrene-butadiene latex, 0.6 part dispersing agent, and 293 parts water.
 3. A paper according to claim 1 wherein the filler product is coated on the paper. 